Price Pfister Multiple Leak?

My Price Pfister bathtub/shower handle is about 12 years old and is the single knob type where you pull it out to start the water and turn to adjust the temperature. Lately, it is VERY difficult to push in the handle all the way. Even in the off position, there is a slow stream of of water coming from the handle itself. This bath is on the 2nd floor and recently I've noticed some water damage on the ceiling of the 1st floor directly below. Is it possible that there is also water leaking behind the wall where the handle is? What is the most likely problem/solution? Thanks for any advice you've got.

Not familiar with the details of your valve, but if you can take the trim off to see the valve, you may be able to see what's leaking. The valve may have a replaceable cartridge. I have used a Price-Pfister valve in two bath remodels and it has a replaceable cartridge that you can order as a service part. Also look behind the wall where the valve is, maybe there is an access panel where you can look inside to see what's going on.

Okay, I'll remove the flange that's behind the handle to see if I can see any leaking back there. Are there any other possible leakage points in the shower/bath setup? I only ask in case the water damage persists after the cartridge replacement.... Also, what if there isn't a replacement cartridge available for my model? Thanks.